The therapeutic and prophylactic uses of compounds which block sympathetic nervous stimulation of .beta.-adrenergic receptors in the heart, lungs, vascular system and other organs are well documented. Typically, such compounds are administered therapeutically to patients suffering from ischemic heart disease or myocardial infarction for the purpose of reducing heart work, i.e., heart rate and contractile force. Reducing heart work reduces oxygen demand, and may also actually increase oxygen supply. Thus reducing heart work can aid in the prevention of further tissue damage and can relieve angina pectoris.
.beta.-Adrenergic stimulation may also aggravate or cause arrhythmias because of increased levels of catecholamines. Thus .beta.-blocking agents may be employed to reduce the risks of arrhythmias.
Compounds in accordance with the present invention selectively block .beta.-adrenergic receptors in various organs. Beta receptors in the heart are generally referred to as .beta..sub.1 receptors, and those associated with vasodilation and bronchodilation are .beta..sub.2 receptors. Selective .beta.-blockers are preferred for the treatment of cardiac disorders, because they may have less potential to cause hypertension or bronchoconstriction. A number of .beta..sub.1 selective adrenergic blocking agents have been discovered [Smith, L. H., J. Appl. Chem. Biotechnol., 28, 201-202 (1978)]. Most such compounds are structural variations of 1-amino-3-aryloxy-2-propanol.
Heretofore, the emphasis in .beta.-blocker research has been to develop compounds which can be administered to cardiac patients over long periods of time. However, often it is desirable in the critical care setting to quickly reduce heart work or improve rhythmicity during a cardiac crisis, e.g., during or shortly after a myocardial infarction. Conventional .beta.-blocking agents can be employed for such treatment, but their duration of action may be much longer than desired by the physician. A .beta.-blocking agent possessing a long duration of action does not allow precise control of heart work or prompt reversal of the .beta.-blocking effect, which may be required in a critical care setting. For instance, if heart output becomes dangerously low, it is desirable to quickly reduce or eliminate .beta.-blocking activity. The lingering activity of available .beta.-blocking agents can be counterproductive and can greatly complicate the therapeutic decisions required of the physician during such critical care of cardiac patients.
Accordingly, there is a need for a pharmaceutical preparation and method of treatment, employing a cardioselective .beta.-adrenergic blocking agent having a short duration of action.
Compounds of the present invention are also useful for the treatment of glaucoma or lowering of intraocular pressure by topical administration of the compounds to the eye. Compounds with short duration in the systemic circulation, but with good stability in ocular fluid, are particularly useful since they have a low potential for producing systemic side effects.
Glaucoma is a condition of the eye characterized by increased intraocular pressure. Untreated, the condition can eventually lead to irreversible retinal damage and blindness. Conventional therapy for glaucoma has involved topical administration of pilocarpine and/or epinephrine, administered to the eye several times daily.
The use of various .beta.-blocking agents to lower intraocular pressure is well documented. For example, U.S. Pat. No. 4,195,085 to Stone discloses a method for treatment of glaucoma by the optical administration of a .beta.-blocking compound, timolol maleate. U.S. Pat. No. 4,127,674 discloses a method of treating glaucoma with labetalol, a known antagonist of both alpha and beta adrenergic receptors. However, these methods also possess significant drawbacks, in that the absorption of the .beta.-blocking compound into the systemic circulation can cause undesirable side effects. Such side effects result from prolonged .beta.-blocking action on the heart, bronchioles and blood vessels. For example, according to Physicians' Desk Reference, Charles E. Baker, Jr., 35th Edition, 1981, p. 1233, adverse reactions to the topical use of timolol maleate can include bronchospasm and heart failure, as well as cardiac conduction defects. Accordingly, there is a need for a method of treatment for glaucoma or for lowering intraocular pressure which is relatively free of unwanted systemic side-effects.
In several copending U.S. patent applications, Ser. No. 211,340 filed Nov. 28, 1980 now abandoned, refiled June 21, 1982 as Ser. No. 390,629, now U.S. Pat. No. 4,450,173; issued May 22, 1984; Ser. No. 276,658 filed June 23, 1981 now U.S. Pat. No. 4,402,974; issued Sept. 6, 1983; and Ser. No. 320,772 filed Nov. 12, 1981 by the owner of the present application, the synthesis and pharmacology of a number of aryloxypropanol amines are described. This work demonstrated that if certain ester and alkyl ester groups are placed on the aryl group that short-acting .beta.-blocking compounds can be obtained; compounds varying in .beta.-blocking potency and cardioselectivity depending upon the position of the ester on the aryl group.